Hyperspectral Classification of Cyperus esculentus Clones and Morphologically Similar Weeds.

Cyperus esculentus (yellow nutsedge) is one of the world's worst weeds as it can cause great damage to crops and crop production. To eradicate C. esculentus, early detection is key-a challenging task as it is often confused with other Cyperaceae and displays wide genetic variability. In this study, the objective was to classify C. esculentus clones and morphologically similar weeds. Hyperspectral reflectance between 500 and 800 nm was tested as a measure to discriminate between (I) C. esculentus and morphologically similar Cyperaceae weeds, and between (II) different clonal populations of C. esculentus using three classification models: random forest (RF), regularized logistic regression (RLR) and partial least squares-discriminant analysis (PLS-DA). RLR performed better than RF and PLS-DA, and was able to adequately classify the samples. The possibility of creating an affordable multispectral sensing tool, for precise in-field recognition of C. esculentus plants based on fewer spectral bands, was tested. Results of this study were compared against simulated results from a commercially available multispectral camera with four spectral bands. The model created with customized bands performed almost equally well as the original PLS-DA or RLR model, and much better than the model describing multispectral image data from a commercially available camera. These results open up the opportunity to develop a dedicated robust tool for C. esculentus recognition based on four spectral bands and an appropriate classification model.

Formulation approaches to reduce post-application pesticide volatilisation from glass surfaces.

Volatilisation is one of the main pathways for pesticide emission to the atmosphere. While formulation strategies and adjuvants are known to affect the fate of active ingredient, no general volatilisation reducing guidelines exist for formulation purposes. Moreover, as limited information on formulation effects is available, current pesticide fate models lack parameters characterising reduction of active ingredient volatilisation. The objective of this study was to investigate the volatilisation reducing potential of formulation types and adjuvants, and to propose an effective vapour pressure for pesticide fate modelling. Several formulations of fenpropimorph, pyrimethanil and tebuconazole were produced and tested in a wind tunnel to evaluate the effect of formulation on active ingredient volatilisation. Produced emulsifiable concentrates with high volatile solvents did not offer any reduction in volatilisation, while the low volatile solvent reduced the volatilisation of pyrimethanil and fenpropimorph with 79.2 and 52.9%, respectively. The microemulsion reduced the volatilisation of fenpropimorph, pyrimethanil and tebuconazole with 57.6, 57.8 and 49.8%, respectively. High surfactant-active ingredient ratios (100:1) reduced the volatilisation of applied amount of pyrimethanil with 50%, on average. The effective vapour pressure of pyrimethanil formulated as a commercial available suspension concentrate was reduced by 33.8%. The commercial available emulsifiable concentrate did not reduce volatilisation of fenpropimorph. Effective vapour pressures of formulated fenpropimorph and pyrimethanil were determined and showed a high correlation with the amount volatilised within 48h. The saturated vapour pressure is useful when comparing the volatility of active ingredients, but effective vapour pressures are more appropriate to be used in pesticide fate models.

Disentangling invasiveness and invasibility during invasion in synthesized grassland communities.

• An experiment with synthesized grassland communities was performed to identify plant traits that contribute to invasiveness and community traits that promote invasibility, and to study the relationship between, and the relative importance of, invasiveness and invasibility. • Eight perennial grass species were used both as invasible monocultures and as potential invaders in gaps in these monocultures. Invasion success in the establishment phase, and invader and monoculture traits were assessed. • Invasion success expressed as germination correlated significantly with germination time (invader trait), light penetration in the gaps and N acquisition by the edge plants (monoculture traits). Success expressed as leaf length correlated with seed mass, germination time (invader traits) and light penetration. Forty-six per cent of the variation in germination was explained by invader identity and 8% by monoculture identity, whereas, for leaf length, they explained 15% and 18%, respectively. • Regenerative traits (seed mass and germination time) correlated with invasiveness, and resource availability (light and nitrogen) with invasibility. The results suggest that species characteristics would largely determine the extent of an invasion event (number of seedlings), while the success of individual invaders (growth and survival) is determined by both species and ecosystem characteristics.

The quantitative and qualitative difference between a F1 hybrid of maize and its F2 generation.

The majority of modern maize varieties are single F1 hybrids. The yield performance of the F2 generation is known to be inferior to the F1 yield performance. We crossed several F1 hybrids and compared these crossings, together with true F2 generations, with the original F1s. Compared to the F1 generation, biomass yield in the F2 generation dropped with -26.7%, and with -8.7% in the crossings. Ear yield dropped with -35.3% and -10.7% respectively. F2 generations had a reduced early vigour and the ear filling startedlater. The yield of some F1 diallel crosses was not significantly different from the yield of the parental F1s.

Vegetation development and floristical diversity of newly created sown and unsown field margin strips on ex arable land during the first 3 successional years.

Early succesion of newly created sown/unsown margin strips on ex arableland, managed by two cuttings per year with/without removal of cuttings was characterised by the replacement of annuals in favour of perennials, a steadily increase in the importance of monocots and a decrease in non N-fixing dicots. Mowing with removal of cuttings delayed this succession pattern. Sorenson's qualitative similarity index (based solely on species occurrence) revealed that species composition of the sown communities (in terms of species occurrence) became increasingly similar to the unsown plots. Furthermore convergence in vegetation composition between sown and unsown plots occurred also in terms of species importance as assessed by Sorenson's quantitative index (based on the combination of species occurrence and importance). Similarity in species importance (but not of species occurrence) was significantly enhanced by cutting with removal of cuttings. During the first 3 successional years, species diversity of sown and unsown communities converged in time, irrespective of mowing regime or location. The decrease in species diversity, number of sown wildflower species and wildflower density of sown communities was more pronounced under a mowing regime without removal of cuttings. The annual addition of mown roadside herbage significantly enhanced species richness but not the importance of dicots.